Adjustable control of power take-off subsystem damping and system thereof

ABSTRACT

The present disclosure provides a method for controlling a power take-off assembly. The method includes providing a drive unit, a transmission having an output, a speed sensor, a controller including a memory unit and a processor, and the power take-off assembly including a clutch and a solenoid. The method also includes storing a first threshold in the memory unit, determining a current input speed of the drive unit with the speed sensor, and comparing the current input speed to the first threshold. The method further includes controlling an amount of hydraulic pressure supplied to the clutch and engaging the clutch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/082,367, filed Nov. 18, 2013, which claims priority to U.S.Provisional Application Ser. No. 61/727,775, filed Nov. 19, 2012 andentitled “Adjustable Control Of Power Take-Off SubSystem Damping,” thedisclosures of which are hereby incorporated by reference in theirentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a system and method for damping noise,and in particular to a system and method of adjustably controlling apower take-off assembly to reduce noise at a no-load idle condition.

BACKGROUND

Conventional internal combustion engines can create significant noisewhen started and running, particularly during idle conditions. Overtime, original equipment manufacturers (OEMs) have desired morestringent noise levels from these engines due to concerns expressed byvehicle owners, whom desire quieter vehicles. As a result, expectationscontinue to get stricter for noise production.

Customers also choose new vehicles that have power take-off capability.A power take-off (PTO) device can be attached to a component of thevehicle, e.g., transmission. The PTO can receive power from an operatingsource, such as an engine, and in turn provide power to an attachment orseparate machine. In this manner, the PTO allows implements to drawenergy from the engine. In some applications, the PTO can be connectedto a vehicle's transmission which is driven by the vehicle's engine. ThePTO can be controlled mechanically, hydraulically, or electrically.

SUMMARY

In one embodiment of the present disclosure, a method is provided forcontrolling a power take-off assembly. The method includes providing adrive unit, a transmission including an output, a speed sensor, acontroller including a memory unit and a processor, and the powertake-off assembly including a clutch, and a solenoid; storing a firstthreshold in the memory unit; determining a current input speed of thedrive unit with the speed sensor; comparing the current input speed tothe first threshold; controlling an amount of hydraulic pressuresupplied to the clutch; and engaging the clutch.

In one example of this embodiment, the controlling step is performed ifthe current input speed is less than the first threshold. In a secondexample, the method includes storing a second threshold in the memoryunit of the controller; determining a load induced on the drive unit;and comparing the load to the second threshold. In a third example, thecontrolling step is performed if the current input speed is less thanthe first threshold and the load is less than the second threshold. In afourth example, the controlling step comprises energizing the solenoid.In a fifth example, the controlling step comprises energizing thesolenoid to supply full hydraulic pressure to the clutch.

In a sixth example, the controlling step comprises energizing thesolenoid to supply partial hydraulic pressure to the clutch. In aseventh example, the method includes detecting if a signal is receivedfrom an operator control switch and performing the controlling andengaging steps if there is no detected signal received. In an eighthexample, the method includes providing a second solenoid; energizing oneof the first solenoid and the second solenoid; and de-energizing theother of the first solenoid and the second solenoid. In a ninth example,the method can also include storing a set of instructions in the memoryunit of the controller for slipping the clutch; repeatedly performingthe determining and comparing steps; and executing the set ofinstructions with the processor so long as the current input speedremains below the first threshold.

In another embodiment of this disclosure, a vehicle includes a driveunit for producing torque, the drive unit including an output; atransmission including an input, a first output, and a second output,wherein the input is coupled to the output of the drive unit; acontroller including a memory unit and a processor, the controllerelectrically coupled to the transmission; a power take-off assemblycoupled to the second output, the power take-off assembly including aclutch and a solenoid electrically coupled to the controller; wherein, aset of instructions is stored in the memory unit of the controller, theset of instructions being executable by the processor to receive acurrent input speed of the drive unit, compare the current input speedto a first threshold, determine if the current input speed is less thanthe first threshold, energize or de-energize the solenoid, and operablycontrol an amount of hydraulic pressure applied to the clutch.

In one example of this embodiment, the set of instructions stored in thememory unit are further executable by the processor to receive a load onthe drive unit, compare the load to a second threshold, and determine ifthe load is less than the second threshold. In a second example, thevehicle includes an operator control switch electrically coupled to thecontroller, the operator control switch configured to be triggered forenabling and disabling the power take-off assembly; wherein, the set ofinstructions stored in the memory unit are further executable by theprocessor to detect if a signal is received from the operator controlswitch and operably control the amount of hydraulic pressure applied tothe clutch if no signal is detected.

In a third example, the set of instructions stored in the memory unitare further executable by the processor to energize the solenoid toapply a maximum amount of hydraulic pressure to the clutch. In a fourthexample, the set of instructions stored in the memory unit are furtherexecutable by the processor to energize the solenoid to apply a reducedamount of hydraulic pressure to the clutch. In a fifth example, thepower take-off assembly comprises an input shaft; an output shaft; afirst drive gear rotatably driven by the second output; a first drivengear rotatably coupled to the input shaft, wherein the first driven gearis rotatably driven by the first drive gear; a second drive gearrotatably coupled to the input shaft; and a second driven gear rotatablycoupled to the output shaft, wherein the second driven gear is rotatablydriven by the second drive gear.

In a different embodiment, a method is provided for controlling ahydraulically-controllable clutch of a power take-off assembly. Themethod includes providing a drive unit, a transmission including anoutput, a speed sensor, a controller including a memory unit and aprocessor, and the power take-off assembly including a clutch and asolenoid; storing a first threshold and a second threshold in the memoryunit; determining a current input speed of the drive unit with the speedsensor; determining a load induced on the drive unit; comparing thecurrent input speed to the first threshold; comparing the load to thesecond threshold; controlling an amount of hydraulic pressure suppliedto the clutch; and engaging the clutch based on the amount of hydraulicpressure supplied thereto.

In one example of this embodiment, the controlling step is performed ifthe current input speed is less than the first threshold, the load isless than the second threshold, and no signal indicative of enabling thepower take-off assembly is received from the operator control switch. Ina second example, the controlling step comprises energizing orde-energizing the solenoid. In a third example, the method can includestoring a set of instructions in the memory unit of the controller forslipping the clutch; repeatedly performing the determining a currentinput speed step of the drive unit with the speed sensor, determining aload induced on the drive unit, comparing the current input speed to thefirst threshold, comparing the current input speed to the firstthreshold, and detecting if a signal indicative of enabling the powertake-off assembly is received from the operator control switch; andexecuting the set of instructions with the processor so long as thecurrent input speed remains below the first threshold, the load remainsbelow the second threshold, and no signal indicative of enabling thepower take-off assembly is received from the operator control switch.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present disclosure and the manner ofobtaining them will become more apparent and the disclosure itself willbe better understood by reference to the following description of theembodiments of the disclosure, taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is an exemplary block diagram and schematic view of oneillustrative embodiment of a powered vehicular system;

FIG. 2 is a perspective view of a portion of a transmission assembly andpower take-off assembly;

FIG. 3 is a control schematic for controlling the clutch of the powertake-off assembly of FIG. 2; and

FIG. 4 is a method of controlling the power take-off assembly of FIG. 2.

Corresponding reference numerals are used to indicate correspondingparts throughout the several views.

DETAILED DESCRIPTION

The embodiments of the present disclosure described below are notintended to be exhaustive or to limit the disclosure to the preciseforms disclosed in the following detailed description. Rather, theembodiments are chosen and described so that others skilled in the artmay appreciate and understand the principles and practices of thepresent disclosure.

Referring now to FIG. 1, a block diagram and schematic view of oneillustrative embodiment of a vehicular system 100 having a drive unit102 and transmission 118 is shown. In the illustrated embodiment, thedrive unit 102 may include an internal combustion engine, diesel engine,electric motor, or other power-generating device. The drive unit 102 isconfigured to rotatably drive an output shaft 104 that is coupled to aninput or pump shaft 106 of a conventional torque converter 108. Theinput or pump shaft 106 is coupled to an impeller or pump 110 that isrotatably driven by the output shaft 104 of the drive unit 102. Thetorque converter 108 further includes a turbine 112 that is coupled to aturbine shaft 114, and the turbine shaft 114 is coupled to, or integralwith, a rotatable input shaft 124 of the transmission 118. Thetransmission 118 can also include an internal pump 120 for buildingpressure within different flow circuits (e.g., main circuit, lubecircuit, etc.) of the transmission 118. The pump 120 can be driven by ashaft 116 that is coupled to the output shaft 104 of the drive unit 102.In this arrangement, the drive unit 102 can deliver torque to the shaft116 for driving the pump 120 and building pressure within the differentcircuits of the transmission 118.

The transmission 118 can include a planetary gear system 122 having anumber of automatically selected gears. An output shaft 126 of thetransmission 118 is coupled to or integral with, and rotatably drives, apropeller shaft 128 that is coupled to a conventional universal joint130. The universal joint 130 is coupled to, and rotatably drives, anaxle 132 having wheels 134A and 134B mounted thereto at each end. Theoutput shaft 126 of the transmission 118 drives the wheels 134A and 134Bin a conventional manner via the propeller shaft 128, universal joint130 and axle 132.

A conventional lockup clutch 136 is connected between the pump 110 andthe turbine 112 of the torque converter 108. The operation of the torqueconverter 108 is conventional in that the torque converter 108 isoperable in a so-called “torque converter” mode during certain operatingconditions such as vehicle launch, low speed and certain gear shiftingconditions. In the torque converter mode, the lockup clutch 136 isdisengaged and the pump 110 rotates at the rotational speed of the driveunit output shaft 104 while the turbine 112 is rotatably actuated by thepump 110 through a fluid (not shown) interposed between the pump 110 andthe turbine 112. In this operational mode, torque multiplication occursthrough the fluid coupling such that the turbine shaft 114 is exposed todrive more torque than is being supplied by the drive unit 102, as isknown in the art. The torque converter 108 is alternatively operable ina so-called “lockup” mode during other operating conditions, such aswhen certain gears of the planetary gear system 122 of the transmission118 are engaged. In the lockup mode, the lockup clutch 136 is engagedand the pump 110 is thereby secured directly to the turbine 112 so thatthe drive unit output shaft 104 is directly coupled to the input shaft124 of the transmission 118, as is also known in the art.

The transmission 118 further includes an electro-hydraulic system 138that is fluidly coupled to the planetary gear system 122 via a number,J, of fluid paths, 140 ₁-140 _(J), where J may be any positive integer.The electro-hydraulic system 138 is responsive to control signals toselectively cause fluid to flow through one or more of the fluid paths,140 ₁-140 _(J), to thereby control operation, i.e., engagement anddisengagement, of a plurality of corresponding friction devices in theplanetary gear system 122. The plurality of friction devices mayinclude, but are not limited to, one or more conventional brake devices,one or more torque transmitting devices, and the like. Generally, theoperation, i.e., engagement and disengagement, of the plurality offriction devices is controlled by selectively controlling the frictionapplied by each of the plurality of friction devices, such as bycontrolling fluid pressure to each of the friction devices. In oneexample embodiment, which is not intended to be limiting in any way, theplurality of friction devices include a plurality of brake and torquetransmitting devices in the form of conventional clutches that may eachbe controllably engaged and disengaged via fluid pressure supplied bythe electro-hydraulic system 138. In any case, changing or shiftingbetween the various gears of the transmission 118 is accomplished in aconventional manner by selectively controlling the plurality of frictiondevices via control of fluid pressure within the number of fluid paths140 ₁-140 _(J).

The system 100 further includes a transmission control circuit 142 thatcan include a memory unit 144. The transmission control circuit 142 isillustratively microprocessor-based, and the memory unit 144 generallyincludes instructions stored therein that are executable by a processorof the transmission control circuit 142 to control operation of thetorque converter 108 and operation of the transmission 118, i.e.,shifting between the various gears of the planetary gear system 122. Itwill be understood, however, that this disclosure contemplates otherembodiments in which the transmission control circuit 142 is notmicroprocessor-based, but is configured to control operation of thetorque converter 108 and/or transmission 118 based on one or more setsof hardwired instructions and/or software instructions stored in thememory unit 144.

In the system 100 illustrated in FIG. 1, the torque converter 108 andthe transmission 118 include a number of sensors configured to producesensor signals that are indicative of one or more operating states ofthe torque converter 108 and transmission 118, respectively. Forexample, the torque converter 108 illustratively includes a conventionalspeed sensor 146 that is positioned and configured to produce a speedsignal corresponding to the rotational speed of the pump shaft 106,which is the same rotational speed of the output shaft 104 of the driveunit 102. The speed sensor 146 is electrically connected to a pump speedinput, PS, of the transmission control circuit 142 via a signal path152, and the transmission control circuit 142 is operable to process thespeed signal produced by the speed sensor 146 in a conventional mannerto determine the rotational speed of the turbine shaft 106/drive unitoutput shaft 104.

The transmission 118 illustratively includes another conventional speedsensor 148 that is positioned and configured to produce a speed signalcorresponding to the rotational speed of the transmission input shaft124, which is the same rotational speed as the turbine shaft 114. Theinput shaft 124 of the transmission 118 is directly coupled to, orintegral with, the turbine shaft 114, and the speed sensor 148 mayalternatively be positioned and configured to produce a speed signalcorresponding to the rotational speed of the turbine shaft 114. In anycase, the speed sensor 148 is electrically connected to a transmissioninput shaft speed input, TIS, of the transmission control circuit 142via a signal path 154, and the transmission control circuit 142 isoperable to process the speed signal produced by the speed sensor 148 ina conventional manner to determine the rotational speed of the turbineshaft 114/transmission input shaft 124.

The transmission 118 further includes yet another speed sensor 150 thatis positioned and configured to produce a speed signal corresponding tothe rotational speed of the output shaft 126 of the transmission 118.The speed sensor 150 may be conventional, and is electrically connectedto a transmission output shaft speed input, TOS, of the transmissioncontrol circuit 142 via a signal path 156. The transmission controlcircuit 142 is configured to process the speed signal produced by thespeed sensor 150 in a conventional manner to determine the rotationalspeed of the transmission output shaft 126.

In the illustrated embodiment, the transmission 118 further includes oneor more actuators configured to control various operations within thetransmission 118. For example, the electro-hydraulic system 138described herein illustratively includes a number of actuators, e.g.,conventional solenoids or other conventional actuators, that areelectrically connected to a number, J, of control outputs, CP₁-CP_(J),of the transmission control circuit 142 via a corresponding number ofsignal paths 72 ₁-72 _(J), where J may be any positive integer asdescribed above. The actuators within the electro-hydraulic system 138are each responsive to a corresponding one of the control signals,CP₁-CP_(J), produced by the transmission control circuit 142 on one ofthe corresponding signal paths 72 ₁-72 j to control the friction appliedby each of the plurality of friction devices by controlling the pressureof fluid within one or more corresponding fluid passageway 140 ₁-140_(J), and thus control the operation, i.e., engaging and disengaging, ofone or more corresponding friction devices, based on informationprovided by the various speed sensors 146, 148, and/or 150.

The friction devices of the planetary gear system 122 are illustrativelycontrolled by hydraulic fluid which is distributed by theelectro-hydraulic system in a conventional manner. For example, theelectro-hydraulic system 138 illustratively includes a conventionalhydraulic positive displacement pump (not shown) which distributes fluidto the one or more friction devices via control of the one or moreactuators within the electro-hydraulic system 138. In this embodiment,the control signals, CP₁-CP_(J), are illustratively analog frictiondevice pressure commands to which the one or more actuators areresponsive to control the hydraulic pressure to the one or morefrictions devices. It will be understood, however, that the frictionapplied by each of the plurality of friction devices may alternativelybe controlled in accordance with other conventional friction devicecontrol structures and techniques, and such other conventional frictiondevice control structures and techniques are contemplated by thisdisclosure. In any case, however, the analog operation of each of thefriction devices is controlled by the control circuit 142 in accordancewith instructions stored in the memory unit 144.

In the illustrated embodiment, the system 100 further includes a driveunit control circuit 160 having an input/output port (I/O) that iselectrically coupled to the drive unit 102 via a number, K, of signalpaths 162, wherein K may be any positive integer. The drive unit controlcircuit 160 may be conventional, and is operable to control and managethe overall operation of the drive unit 102. The drive unit controlcircuit 160 further includes a communication port, COM, which iselectrically connected to a similar communication port, COM, of thetransmission control circuit 142 via a number, L, of signal paths 164,wherein L may be any positive integer. The one or more signal paths 164are typically referred to collectively as a data link. Generally, thedrive unit control circuit 160 and the transmission control circuit 142are operable to share information via the one or more signal paths 164in a conventional manner. In one embodiment, for example, the drive unitcontrol circuit 160 and transmission control circuit 142 are operable toshare information via the one or more signal paths 164 in the form ofone or more messages in accordance with a society of automotiveengineers (SAE) J-1939 communications protocol, although this disclosurecontemplates other embodiments in which the drive unit control circuit160 and the transmission control circuit 142 are operable to shareinformation via the one or more signal paths 164 in accordance with oneor more other conventional communication protocols (e.g., from aconventional databus such as J1587 data bus, J1939 data bus, IESCAN databus, GMLAN, Mercedes PT-CAN).

In one example of the vehicular system 100, a PTO (not shown) can beconnected to the transmission via an input gearset for receivingmechanical power. The PTO can also include an internal, transfergearset. Each gearset (i.e., the input and transfer) can include a firstand a second gear for delivering and receiving power, respectively. Withrespect to the input gearset, a corresponding gear or mechanism of thePTO can interact with a gear or mechanism of the transmission to receiveand transfer power. The interacting gears of either gearset, however,can create a low load or speed rattle noise due to the inherent backlashbetween gears. The noise can be particularly noticeable when the engineis operating at a low speed or idle condition and when there is no loadon the PTO. To reduce or overcome this noise, engine or transmissiondesigns, specifically their mass/elastic systems, can be changed oradditional hardware (e.g., an isolator gear) may be incorporated intothe current design. These changes, which can affect the mass/elasticsystem, can be very costly and have a limited effectiveness to thisparticular PTO powertrain mass/elastic combination.

Therefore, a need exists for a more cost effective and global solutionby controlling the damping within the power take-off subsystem to reduceor eliminate noise at or approximate to a no-load idle condition.

Referring to FIG. 2, one example is shown of a transmission and PTOassembly. As described above, a PTO is a device that can redirect aportion of the input power provided by a prime mover (e.g., an engine)to tools, work implements, or accessories for the purpose of performingfunctions which are secondary to the purpose for the power pack. Forinstance, the PTO could provide power to a hydraulic pump. In a hybridsystem application, however, power or torque can flow in both directions(i.e., between inputs and outputs, rather than from an input to anoutput).

In FIG. 2, a prime mover 200 is provided having a propulsion shaft 202for delivering power to a transmission assembly 206. The transmissionassembly 206 can be mounted to a flex plate 204 of the prime mover 200.The transmission assembly can include a torque converter 208 coupled tothe shaft 202. The propulsion shaft 202 in FIG. 2 can correspond withthe output shaft 104 of FIG. 1. The torque converter 208 can have apiston 210, back plate 212 and pump 214 operably disposed in an outershell for torque multiplication. The torque converter 208 can be coupledto a drive shaft 216 of the transmission assembly 206. Referring to FIG.1, the drive shaft 216 can correspond with shaft 116.

The drive shaft 216, or PTO drive shaft, can include splines 218 forcoupling to the torque converter 208 and a PTO drive gear 226. At an endopposite of the torque converter 208, a pump 224 can be coupled to thedrive shaft 216. A portion of a drive hub 222 is positioned near thepump 224. The drive gear 226 can be coupled to the drive shaft 216 fortransferring torque to a power take-off (PTO) assembly 232. The drivegear 226 is disposed between a pair of bearings 220 as shown.

The PTO assembly 232 can include an input gearset as shown in FIG. 2.The input gearset includes a first input gear 228 coupled to the drivegear 226. In particular, the teeth of the first input gear 228 can becoupled with the drive gear 226 of the transmission assembly 206 so thattorque is transferred to the PTO assembly 232 from the transmissionassembly 206. The first input gear 228 can be disposed about a spindle230 which can further transfer torque to an output gearset. The outputgearset, which forms part of the PTO assembly 232, can include a secondinput gear 244 that is disposed about the spindle 230 adjacent to thefirst input gear 228. The second input gear 244 can be further coupledto an output gear 234 of the PTO assembly 232. The output gear 234 canbe coupled to an output shaft 236 of the PTO assembly 232 to delivertorque to an implement or attachment coupled thereto. Moreover, bearingsand seals 240, 242 can provide lubrication and support to the gears andshafts of the PTO assembly 232.

As further shown in FIG. 2, the PTO assembly 232 can disconnect itsinput gearset from its output shaft by including an electricallycontrolled hydraulic clutch 238 (i.e., a PTO clutch 238) instead of amechanical or sliding gear type. This power shift PTO assembly 232,which has the internal hydraulic clutch 238, can therefore be engagedindependently from, but in coordination with, the operating conditionsperformed by the transmission power pack. The PTO can include a controlsystem that is independent of the control system of the transmission.However, via electronic communications between the power pack, theoperator, and the PTO, the PTO is engaged or disengaged when desired bythe operator, and under the appropriate conditions with the power packoperation.

Referring to FIG. 2, power can be transferred between the power pack ofthe transmission assembly 206 and the PTO assembly 232 via the inputgearset (i.e., gears 226, 228), and then, transferred to the outputshaft 236 of the PTO assembly 232 by the output gearset (i.e., gears244, 234). Alternatively, transfer gearsets can be provided to allow therelationship between the speed of the prime mover 200 and the outputshaft 236 of the PTO assembly 232 to be appropriately selected dependingon the specific requirements and operational conditions for theimplements to be driven by the PTO assembly 232. The transfer of powerbetween the prime mover 200, the power pack of the transmission assembly206, and PTO assembly 232 can be a direct mechanical connection in orderfor the operator to directly control the output speed of the PTO.However, in other examples, the transfer of power can be via an indirectmechanical connection for controlling the PTO. For instance, in one suchembodiment, the indirect connection can be made only when the lockupclutch 136 is engaged.

The requirement for a direct drive connection may also allow thevariable rotation and torque characteristics, which are inherent tointernal combustion prime movers 200 and created by the independentfiring of each of its cylinders, to also be transmitted through theinput gearset and output gearset of the PTO assembly 232. Since mostgearsets also inherently have some amount of backlash, this uneven orvibratory rotational movement can cause these gearsets to rattle whenthe PTO assembly 232 is not engaged and is not transmitting a torqueload to the implement which it drives. This rattle noise can beundesirable and may raise the level of noise generated by the overallpower pack installation when it is at an idle, no load condition.

As described above, hardware and design features within the power packwhich may reduce the level of this noise to near acceptable levels canbe costly and difficult to implement within existing power pack designs.Moreover, to reduce the noise a design change must be robust enough toaccount for the characteristics of existing and future prime movers,numerous mass/elastic configurations for the power pack as well as thevarious available PTO designs, and the load requirements for theimplements to be driven. However, many hardware or design changes areoften limited to the configurations for which they were designed, or inother words, are generally “tuned” to the characteristics of the primemover and the mass/elastic systems for which they were designed.

In addition, the internal drag or torque required to turn the PTOassembly 232 at a no load, idle condition can vary depending on theinternal PTO assembly design and production process control tolerancesfor items such as bearing clearances, oil shaft seal contacts, andclutch clearance. Furthermore, because of fuel economy considerations,these features are typically optimized in order to reduce the amount ofPTO damping which conflicts with the design direction needed to resolvethe noise issue.

Thus, to reduce the noise without altering the design of the power packof the transmission assembly 206 or the PTO assembly 232, the internalPTO hydraulic clutch 238 can be electrically controlled. In doing so,the clutch 238 can be partially applied to provide an adequate amount ofdrag to prevent unacceptable gear rattle. For instance, in onenon-limiting example, approximately 8 psi of clutch pressure can behydraulically applied to the PTO clutch 238 to induce about 3.6 N-m ofdrag in the PTO hydraulic clutch 238. Under these conditions, thepartial apply can reduce the noise level to an acceptable level.

Turning to FIG. 3, a control schematic 300 illustrates an embodiment forcontrolling the clutch pressure of the PTO clutch 238. Here, acontroller 302 is shown having at least a first wire 308 and a secondwire 310 electrically coupled to a PTO assembly 312. The controller 302can perform in a similar manner as the transmission control circuit 142of FIG. 1. In other words, the controller 302 can include a memory unitfor storing a set of instructions that can be executed by a processor.The controller 302 can store torque curves, look-up tables, shiftcurves, and any other algorithms, methods, processes, or set ofinstructions for controlling the PTO clutch 238. The controller 302 canbe in electrical communication with the transmission 118 via a firstcommunication link 318.

The controller 302 can also be in electrical communication with operatorcontrols 304 via a second communication link 320. The operator controls304 can include a manual shift selector 304, for example, that includesa plurality of user controls. The operator controls 304 can include aplurality of switches, buttons, levers, joysticks, pedals, etc. In FIG.3, one of the plurality of operator controls can include a PTO controlbutton 306. The operator controls can be disposed in a cab of a vehicleto allow the vehicle operator to manually select one or more of the usercontrol buttons on the operator controls 304. In particular, the vehicleoperator can select the PTO control button 306 to transfer torque from adrive unit to the output of the PTO assembly 312 via the transmission118 and a connection 322 between the transmission 118 and PTO assembly312. When the PTO control button 306 is triggered to an active orenabled state, a signal is electrically transmitted to the controller302 to indicate that the operator desires to activate or enable the PTOassembly 312. There can be specific circumstances and conditions underwhich the PTO assembly 312 can be enabled, and the controller 302 canstore these conditions in its memory unit. Thus, when the PTO controlbutton 306 is triggered and the controller 302 receives the indicativesignal from the operator controls 304, the controller 302 can determinewhether appropriate conditions are satisfied before activating orenabling the PTO assembly 312.

The PTO assembly 312 can include an electrical control system in theform of an adjustable solenoid, pressure switch, valve, etc. In oneexample, the control system can include two single stage solenoids. Inanother example, the control system can include a variable bleedsolenoid. In a further example, the control system can include atwo-stage solenoid. In the illustrated example of FIG. 3, the controlsystem can include a first solenoid 314 and a second solenoid 316. Eachof the first solenoid 314 and second solenoid 316 can be electricallycoupled to the controller 302 via the electrical wires 308, 310. Anelectrical signal can be submitted to or from the controller 302 and PTOassembly 312 to enable or disable the solenoids.

The first solenoid 314 can be electrically enabled during a full powercondition and the second solenoid 316 can be electrically enabled duringa partial power condition. For purposes of this disclosure, the “fullpower condition” may refer to when a full clutch pressure is applied tothe PTO clutch 238 to deliver mechanical power to the PTO output andmechanically drive an attachment or implement coupled to the PTOassembly 312. Moreover, the “partial power condition” may refer to whena partial clutch pressure is applied to the clutch 238 to create drag inthe clutch for reducing the noise output at a no-load, idle condition.

The clutch pressure can be supplied by a PTO control assembly 324 of thePTO assembly 312. The PTO control assembly 324 can include valves,solenoids, etc. for adjustably controlling the amount of hydraulicpressure supplied to the PTO clutch 238. The PTO control assembly 324can be operably controlled based on the electrical state of the firstsolenoid 314 and the second solenoid 316. This can allow for adjustablecontrol of the amount of drag in the clutch for different applications.As such, the amount of damping can be adjustably controlled by theamount of clutch pressure commanded and delivered to the controlassembly 324 of the PTO assembly 312. In this embodiment, the controller302 not only can supply a signal for the normal operation of the PTO butcan also supply an additional signal to the PTO control assembly 324when drag is no longer required.

For example, once engine or input speed exceeds a threshold speed, e.g.,850 RPM, a signal can be communicated to the control assembly 324 of thePTO assembly 312 to disable the partial apply and clutch slipping. Thismay be desirable to prevent excessive fuel economy loss.

The PTO clutch 238 can be designed to handle different periods ofslipping over time during the appropriate conditions (i.e., low speedsat or near idle and under no implement load). Clutch friction plates,for example, have been designed with a carbon fiber material and used inthe automotive industry for several years in order to preventtransmitting the same uneven torque and input rotation from internalcombustion engines which causes torsional activity and damage withinvehicle transmissions. As a result, similar carbon fiber frictionmaterial may be incorporated into the PTO clutch design to enable theappropriate amount of clutch slipping to reduce noise at or near ano-load, idle condition.

Referring to FIG. 4, an example is provided of a method 400 forcontrolling the amount of hydraulic pressure supplied to the PTO clutch238. The method 400 can include a plurality of blocks that are stored inthe memory unit and executed by the processor in the controller 302 foroperably controlling the PTO clutch 238. The plurality of blocksillustrated in FIG. 4 is not intended to be limiting, as one differentexample may include fewer blocks and a second different example mayinclude additional blocks.

In any event, the method 400 can include a first block 402 that isexecuted by the processor to determine a current input speed of thedrive unit 102. Here, the controller 302, which can take a form similarto that of the transmission control circuit 142 of FIG. 1, can receiveinput speed over a signal path 164, such as J-1939. In another example,a speed sensor 146 can detect the input speed of the drive unit 102 andsend it to the controller 302 via a communication link 152. There can beother conventional means for receiving input speed so that the processoris able to execute block 402.

Once block 402 is executed, the method 400 can advance to block 404where the processor can execute block 404 by comparing the current inputspeed of the drive unit 102 with a speed threshold. The speed thresholdcan be a single value or a range of values stored in the memory unit ofthe controller 302. Alternatively, the speed threshold may be dependenton various factors and therefore is determined from a look-up table,curve, etc. Once the controller 302 determines the speed threshold, theprocessor can compare the current input speed to the speed threshold inblock 404. Moreover, the processor can execute block 406 by determiningwhether the current input speed is less than the speed threshold. Inthis manner, the controller 302 can determine whether the drive unit isoperating at or near an idle condition. In one non-limiting example, thespeed threshold can be 850 RPM. If the current input speed is less thanspeed threshold, the method can advance to block 408. If, however, thecurrent speed is greater than the speed threshold, the method can returnto block 402 and repeat the conditions set forth therein.

In block 408, the controller 302 can determine a current load on thedrive unit 102. The load can be determined by any conventional means,including receiving inputs from different sensors, measuring the load,estimating the load, etc. An inclinometer, for example, can measure roadgrade and send a signal to the controller 302 with the measured roadgrade. In another aspect, the load can be determined as a function ofthrottle position or a percentage by which an accelerator pedal isdepressed. In FIG. 3, the controller 302 can receive throttle positionfrom a throttle input source, which can be coupled to the drive unitcontrol circuit 160 of FIG. 1 for transmitting throttle data over adatalink (e.g., signal path 164). Examples of a conventional datalinkinclude J1587 datalink, J1939 datalink, IESCAN datalink, Hardwire TPS(throttle position sensor) to TCM, and Hardwire PWM (pulse widthmodulation) to TCM. Unlike drive unit torque data, for example, which iscommunicated from the ECM to the TCM, throttle data can be communicatedover the datalink and is not limited to a particular drive unit orengine/transmission configuration. Instead, the datalink can be adaptedto most vehicle setups.

In any event, once the current load or throttle position is known, themethod 400 can advance to block 410 where the processor compares theload or throttle position to a different threshold (e.g., load orthrottle threshold). The load or throttle threshold can be stored in thememory unit of the controller 302 in a manner similar to that of thespeed threshold. The result of block 410 is further determined in block412. Here, if the load or throttle is less than the load or throttlethreshold, the controller 302 can determine that there is no load orthat the actual throttle position is less than a predefined amount(e.g., percentage), or an approximately small load, on the drive unit.In this case, the method 400 can advance to block 414. In the event theload is greater than the load threshold in block 412, the method 400 canreturn to block 402.

In block 414, the controller 302 can determine whether a signal has beentriggered from the PTO control button or switch 306 to request anenablement or activation of the PTO assembly 312. If the PTO controlbutton or switch 306 has been triggered to an enabled or active state,the controller 302 can either decide whether to activate the PTOassembly 312 (based on the conditions set forth above) or maintain thePTO assembly 312 disabled. In any event, if the PTO control button 306is enabled, method 400 can advance to block 402. Alternatively, if thePTO control button 306 remains disabled, method 400 can advance to block416.

Although method 400 shows blocks 408, 410, 412, and 414, in otherexamples the method 400 may only determine input speed in block 402 andcompare it to the speed threshold in block 404. Once the method advancesto block 416, the processor can execute block 416 by further executing aPTO clutch slip process which is stored in the memory unit. The clutchslip process can desirably control the amount of hydraulic pressuresupplied to the PTO clutch 418. Once the PTO clutch slip process isenabled in block 416, the method 400 can advance to block 418 where thecontroller 302 can control the amount of pressure supplied to the PTOclutch 238 by energizing and de-energizing the first solenoid 314 andthe second solenoid 316.

As described above, the first solenoid 314 can be electrically enabledduring a full power condition and the second solenoid 316 can beelectrically enabled during a partial power condition. Thus, when thecontroller 302 determines a condition equivalent to full clutch pressureis needed, the first solenoid 314 can be energized. When it is moredesirable to slip the clutch 238, and thus reduce the noise from the PTOassembly 312, the controller 302 can energize the second solenoid 316.When the second solenoid 316 is energized, the partial or reduced clutchpressure applied to the PTO clutch 238 can create sufficient drag in theclutch for reducing the noise output at an approximate no-load, idlecondition.

Method 400 can advance to block 420 before, during, or after theexecution of block 418. In particular, in block 420, the method returnsto block 402 where the controller 302 determines the current input speedof the drive unit 302. In this manner, the controller 302 can repeatedlyand continuously execute blocks 402, 404, and 406 to ensure that thedrive unit is at or near the idle condition. Moreover, the controllercan repeatedly and continuously monitor the load on the drive unit inblocks 408, 410, and 412 to ensure that the drive unit remainssubstantially unloaded and also monitor the state of the PTO controlbutton 306 in block 414 as method 400 is executed. In the event theconditions set forth in either block 406 or block 412 is no longer true,or the PTO control button 306 is enabled, the second solenoid 316 can bede-energized and the PTO clutch 238 can either be controlled under fullhydraulic pressure or no hydraulic pressure.

In a related embodiment, the PTO assembly 312 can include only a singlevariable bleed or variable control mechanism. The variable controlmechanism can be a solenoid or other mechanism for controlling anelectric-to-hydraulic control PTO clutch 238. In this embodiment, theamount of current or voltage supplied by the controller 302 to thevariable control mechanism can control the amount of hydraulic pressuresupplied to the PTO clutch 236. In other words, a lower current orvoltage may induce a reduced amount of pressure supplied to the PTOclutch 236 in order to slip the clutch 236. A greater current or voltagemay induce approximately full pressure to the clutch 236. Othervariations and aspects are contemplated by this variable control of thePTO assembly 312.

In another aspect or embodiment of the present disclosure, a geartrain(i.e., a direct mechanical drive without any hydraulic coupling), mayinclude a PTO that causes or induces an audible rattle noise conditionwhen it is not under a direct load due to backlash between interfacinggears. The noise may further be attributed to torque associated with theinertia of the unloaded geartrain and the periodic firing of thecylinders of an internal combustion engine or drive unit. By introducinga small amount of damping to the geartrain or system, the slipping of anelectronically-controlled, hydraulic clutch of the PTO can reduce oreliminate the noise. The clutch may be positioned internally within thePTO, for example.

In addition, there are a variety of gear and clutch combinations as wellas a variety of control methods by which this damping activity can beaccomplished. The transmission or engine controller can be used forsoftware memory and monitoring of the conditions under which thisactivity is controlled, or the accessory (e.g., PTO) can have it ownscontroller. The pressure to slip the clutch can be provided by aplurality of configurations of solenoids, or electric-over-hydraulicdevices. The clutch design is structurally durable to allow for timeduring which it will slip at less than a full apply pressure.Conventional, carbon fiber friction plate material can be used in thedesign to provide desired durability of the clutch. There may be manydifferent conditions under which the clutch slips due to a lowerhydraulic pressure supplied thereto, but these conditions may bepredefined as a set of instructions or algorithm in one of thecontrollers (e.g., transmission control unit) and thereby monitoredelectronically.

While exemplary embodiments incorporating the principles of the presentdisclosure have been disclosed hereinabove, the present disclosure isnot limited to the disclosed embodiments. Instead, this application isintended to cover any variations, uses, or adaptations of the disclosureusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this disclosure pertains andwhich fall within the limits of the appended claims.

1. A method for controlling a power take-off assembly, comprising:providing a drive unit, a transmission including an output, a speedsensor, a controller including a memory unit and a processor, and thepower take-off assembly including a clutch, a first solenoid and asecond solenoid; storing a first threshold in the memory unit;determining a current input speed of the drive unit with the speedsensor; comparing the current input speed to the first threshold;controlling an amount of hydraulic pressure supplied to the clutch; andengaging the clutch by energizing one of the first solenoid or thesecond solenoid.
 2. The method of claim 1, wherein the controlling stepis performed if the current input speed is less than the firstthreshold.
 3. The method of claim 1, further comprising: storing asecond threshold in the memory unit of the controller; determining aload induced on the drive unit; and comparing the load to the secondthreshold.
 4. The method of claim 3, wherein the controlling step isperformed if the current input speed is less than the first thresholdand the load is less than the second threshold.
 5. The method of claim1, wherein the controlling step comprises energizing one of the firstsolenoid or the second solenoid based on the comparing step.
 6. Themethod of claim 1, wherein the controlling step comprises energizing thefirst solenoid to supply full hydraulic pressure to the clutch.
 7. Themethod of claim 1, wherein the controlling step comprises energizing thesecond solenoid to supply partial hydraulic pressure to the clutch. 8.The method of claim 1, further comprising: detecting if a signal isreceived from an operator control switch; and performing the controllingand engaging steps if there is no detected signal received.
 9. Themethod of claim 1, further comprising: energizing one of the firstsolenoid and the second solenoid; and de-energizing the other of thefirst solenoid and the second solenoid.
 10. The method of claim 1,further comprising: storing a set of instructions in the memory unit ofthe controller for slipping the clutch; repeatedly performing thedetermining and comparing steps; and executing the set of instructionswith the processor so long as the current input speed remains below thefirst threshold.
 11. A vehicle, comprising: a drive unit for producingtorque, the drive unit including an output; a transmission including aninput, a first output, and a second output, wherein the input is coupledto the output of the drive unit; a controller including a memory unitand a processor, the controller electrically coupled to thetransmission; and a power take-off assembly coupled to the secondoutput, the power take-off assembly including a clutch and a solenoidelectrically coupled to the controller; wherein, a set of instructionsis stored in the memory unit of the controller, the set of instructionsbeing executable by the processor to receive a current input speed ofthe drive unit, compare the current input speed to a first threshold,determine if the current input speed is less than the first threshold,fully energize or de-energize the solenoid, and operably control anamount of hydraulic pressure applied to the clutch.
 12. The vehicle ofclaim 11, wherein the set of instructions stored in the memory unit arefurther executable by the processor to receive a load on the drive unit,compare the load to a second threshold, and determine if the load isless than the second threshold.
 13. The vehicle of claim 11, furthercomprising an operator control switch electrically coupled to thecontroller, the operator control switch configured to be triggered forenabling and disabling the power take-off assembly; wherein, the set ofinstructions stored in the memory unit are further executable by theprocessor to detect if a signal is received from the operator controlswitch and operably control the amount of hydraulic pressure applied tothe clutch if no signal is detected.
 14. The vehicle of claim 11,wherein the set of instructions stored in the memory unit are furtherexecutable by the processor to fully energize the solenoid to apply amaximum amount of hydraulic pressure to the clutch.
 15. The vehicle ofclaim 11, wherein the set of instructions stored in the memory unit arefurther executable by the processor to energize a second solenoid toapply a reduced amount of hydraulic pressure to the clutch.
 16. Thevehicle of claim 11, wherein the power take-off assembly comprises: aninput shaft; an output shaft; a first drive gear rotatably driven by thesecond output; a first driven gear rotatably coupled to the input shaft,wherein the first driven gear is rotatably driven by the first drivegear; a second drive gear rotatably coupled to the input shaft; and asecond driven gear rotatably coupled to the output shaft, wherein thesecond driven gear is rotatably driven by the second drive gear. 17.Power take-off assembly, comprising: an input shaft configured totransfer torque to the power take-off assembly from a drive unit; anoutput shaft having coupler on one end; a hydraulic clutch disposedbetween the input shaft and the output shaft, the hydraulic clutchhaving a fully engaged position, a partially engaged position, and adisengaged position; a first solenoid having an open state where thefirst solenoid is fluidly coupled to the hydraulic clutch and having aclosed state where the first solenoid is not fluidly coupled to thehydraulic clutch; and a second solenoid having an open state where thesecond solenoid is fluidly coupled to the hydraulic clutch and having aclosed state where the second solenoid is not fluidly coupled to thehydraulic clutch; wherein, when the hydraulic clutch is in the fullyengaged position, the first solenoid is in the open state and the secondsolenoid is in the closed state.
 18. The power take-off assembly ofclaim 17, wherein when the hydraulic clutch is in the partially engagedposition, the second solenoid is in the open state and the firstsolenoid is in the closed state.
 19. The power take-off assembly ofclaim 17, wherein when the hydraulic clutch is in the disengagedposition, the first solenoid and the second solenoid are in the closedstate.
 20. The power take-off assembly of claim 17, further comprising:a controller having a memory unit and a processor that is electronicallycoupled to the first solenoid and the second solenoid, the memory unitstoring a threshold value; and a sensor electronically coupled to thecontroller and configured to measure the rotational speed of the inputshaft; wherein, the sensor communicates the rotational speed of theinput shaft to the controller and the controller compares the rotationalspeed to the threshold and transitions the hydraulic clutch to eitherthe fully engaged position, the partially engaged position, or thedisengaged position based on the comparison.